In modem marine seismic streamer systems, a vessel tows a long cable supporting a large number of sensors. Recent developments in such systems have simultaneously focused on making them light, durable, and easy to manufacture and maintain, as well as sensitive to the acoustic signals of interest while remaining relatively immune to noise. These developments lead to improvements disclosed in U.S. Pat. No. 6,128,251, assigned to the same assignee as the present invention.
In U.S. Pat. No. 6,128,251, there was disclosed a structure of a solid marine seismic cable which included an interior cable, a surrounding woven strength member, an overlying foam floatation layer, and an enclosing jacket. One or more elongate channels were formed in the overlying floatation layer, and one or more piezoelectric elements were mounted in the channel(s). The elongate channel enlarges the acoustic aperture for improved reception of seismic signals.
Further testing of the structure disclosed in that patent proved the efficacy of the structure disclosed therein, and has resulted in certain improvements and refinements, which are the focus of the present application. More particularly, we have continued to develop the acoustic aperture of the channels disclosed in that patent, especially regarding noise and its origins and effects. We have found that, contrary to standard assumptions regarding previous liquid filled and solid marine seismic cables, noise is not uniformly distributed around the cable at the hydrophones. This discovery has lead to the development of the embodiments disclosed herein.